Originally posted on Google Apps Developer Blog
Posted by Saurabh Gupta, Product Manager, Google Apps Script
Back in December 2014, we announced the IFRAME sandbox mode for HtmlService which has helped improve the speed of an application’s user interface (UI). It also gives users a choice of using a variety of JS libraries on the client. We have been working hard to improve IFRAME sandbox mode and have added many features since then, including: Firefox support, file uploads, top navigation support, and improved Google Picker API support. Since IFRAME sandbox provides faster UIs and has more capabilities than NATIVE and EMULATED modes, developers should only be using IFRAME sandbox mode moving forward.
As of today, both EMULATED and NATIVE modes in HtmlService are deprecated. Over the next few months, we plan on sunsetting both EMULATED and NATIVE modes in stages to give you enough time to migrate your scripts.
We have created a migration guide to help you with this transition. For many scripts, no changes will be needed, unless they use a small set of features described in the migration guide. The guide also describes a few potential breaking changes. It is important that you review all your scripts that use HtmlService to ensure that the switch to IFRAME sandbox mode does not cause them to fail.
Here’s the timeline:
In November 2015, all new scripts will default to IFRAME sandbox mode unless NATIVE mode is explicitly specified. For example, if you make a copy of an existing script, the new script will use IFRAME sandbox mode unless you have explicitly set the sandbox mode to NATIVE.
In December 2015 (see sunset schedule for exact dates), EMULATED mode will be shutdown. Any scripts explicitly using EMULATED mode will default to IFRAME sandbox mode.
On April 28th, 2016, all scripts will default to IFRAME sandbox unless you have explicitly specified NATIVE mode in your script. For example, if your script has not specified any mode, then it will change from using NATIVE mode to IFRAME sandbox mode. Please make sure that your UI works well in IFRAME sandbox mode.
On June 30th 2016, NATIVE mode will be shutdown. All scripts explicitly using NATIVE mode will default to IFRAME sandbox mode.
While deprecations may at times seem inconvenient, this staged deprecation should ease in the migration process. Our goal is to provide a modern and secure environment enabling developers to create great apps for their users with Google Apps Script.